Cement suitable for coal bed gas cementing and its preparation method

Abstract

The application discloses cement suitable for coal bed gas well cementation and a preparation method thereof, and the cement comprises the following components in percentage by weight: G-grade cement 55-75 wt%, active mineral material 15-20 wt%, composite reinforcing material 3-5 wt%, lightening agent 5-15 wt%, fluid loss reducer 1-3 wt% and dispersant 1-2 wt%. The cement suitable for coal bed gas well cementation has excellent construction performance at low temperature, rapid strength development, good channeling prevention performance and toughness, and the like. A large amount of solid waste is selected as a raw material for preparation, so that the solid waste consumption is improved, land resource waste and environmental pollution caused by solid waste storage are reduced, and the application has the characteristics of green environmental protection, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of cementing technology in oil and gas field development, specifically to a cement suitable for cementing coalbed methane and its preparation method. Background Technology

[0002] my country is rich in coalbed methane resources. In recent years, with the gradual formation of the domestic coalbed methane industrial development, coalbed methane has become an important part of my country's petroleum energy. The main characteristics of coalbed methane wells are shallow gas layers, low bottom-hole temperatures (generally between 25℃ and 45℃), low coal seam permeability, and low pore pressure. Therefore, low-density cement slurry systems are commonly used for well cementing.

[0003] Patent CN110054440A discloses a low-temperature, early-strength, low-density cement slurry system for coalbed methane cementing. The raw material components and their weight contents of the cement slurry system are as follows: oil well cement: 430 parts; slag powder: 430 parts; fly ash: 140 parts; cenospheres: 0-140 parts; fluid loss reducer: 28-32 parts; early-strength agent: 10-12 parts; expansion agent: 4-6 parts; dispersant: 10-12 parts; retarder: 6-8 parts; water: 600-920 parts.

[0004] Patent CN104194752A discloses a low-temperature early-strength agent for cementing coalbed methane wells and a cement slurry containing the agent. The low-temperature early-strength agent has the following composition: 1.5-2.5 parts by weight of calcium formate, 0.20-0.80 parts by weight of calcium sulfate, 0.30-1.0 parts by weight of aluminum sulfate, 0.20-1.0 parts by weight of sodium silicate, 0.20-0.80 parts by weight of sodium sulfate, 0.10-0.60 parts by weight of sodium aluminate, and 0.30-0.80 parts by weight of carbon nanotubes.

[0005] Current research on cement for coalbed methane well cementing is limited, and existing cement slurry systems have significant shortcomings. In low-temperature environments, the slow hydration rate of cement leads to prolonged setting time, increasing the risk of annular channeling, slow strength development, low early strength, and poor toughness. Therefore, to meet the needs of coalbed methane well cementing development, developing a low-density cement system with low-temperature rapid setting, low water loss, high early strength, anti-channeling properties, and high toughness is crucial for the development and utilization of coalbed methane. Summary of the Invention

[0006] In order to overcome the defects and shortcomings of the existing technology, the present invention provides a cement suitable for coalbed methane cementing and its preparation method, so as to solve the problems of slow early strength development, large water loss, poor toughness and poor anti-channeling performance of cement slurry in low temperature environment of coalbed methane cementing.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a cement suitable for cementing coalbed methane wells, comprising the following raw materials by weight percentage:

[0009] Grade G cement: 55-75 wt%;

[0010] Active mineral materials: 15-20 wt%

[0011] Composite reinforcement material: 3-5 wt%

[0012] Lightening agent: 5-15 wt%

[0013] Water loss reducing agent: 1-3 wt%;

[0014] Dispersant: 1-2 wt%.

[0015] Furthermore, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag, and wollastonite powder in a mass ratio of 3:2:1:1.

[0016] Furthermore, the fly ash contains 40-50 wt% SiO2 and 35-45 wt% Al2O3; the microsilica contains 96 wt% SiO2 and has a particle size of 0.05-0.30 μm; the lithium mica ore slag contains 50-60 wt% SiO2, 25-30 wt% Al2O3, and 3-5 wt% CaSO4; and the wollastonite powder contains >50 wt% SiO2, >40 wt% CaO, and has an average particle size of 50 μm.

[0017] Furthermore, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of (14-16):(2-3):(2-3).

[0018] Furthermore, the early-strength material is prepared by mixing active component A, active component B, and reinforcing component in a mass ratio of 1:3:1, and the preparation method is as follows:

[0019] S1. Mix the active component A and the reinforcing component to obtain powder A;

[0020] S2. Place active component B in a ball mill jar and ball mill at 500 rpm for 6 hours to obtain powder B;

[0021] S3. Powder A and powder B are pneumatically mixed to obtain early strength material;

[0022] The early-strength material of this invention provides an alkaline environment for the initial hydration reaction of cement, thereby promoting the cement hydration reaction and activating the activity of active component B, facilitating the decomposition of solid waste residue in active component B, and promoting the Si... 4+ Al3+ and Ca 2+ Plasma release accelerates the formation of hydration products. Furthermore, in this invention, active component A acts as a seed crystal for hydrated calcium silicate and hydrated calcium aluminosilicate in the early stages of hydration, providing a good nucleation effect during cement hydration, inducing the formation of hydrated calcium silicate and hydrated calcium aluminosilicate during cement hydration, promoting cement hydration, and thus improving the early strength of cement.

[0023] Preferably, the active component A is prepared by mixing carbide slag, biomass slag, and aerated concrete waste in a mass ratio of 5:4:1, and the preparation method is as follows:

[0024] S11. Place carbide slag, biomass slag and aerated concrete waste in a ball mill jar at a mass ratio of 5:4:1, with a liquid-to-material ratio of 1.0, and ball mill at 400 rpm for 72 hours to obtain slurry A.

[0025] S12. Place slurry A in a sealed mixing tank, add 1 wt% of the dispersant and stabilizer from the solid phase of slurry A and stir. The stirring temperature is 80℃ and the stirring time is 72h to obtain slurry B.

[0026] S13. Place slurry B in a centrifuge for liquid-solid separation, and dry the solid phase at the bottom of the liquid-solid separation into dry powder to obtain active component A;

[0027] More preferably, the calcium carbide slag contains 65-70 wt% CaO and has a pH of 12-13; the biomass slag contains ≥65 wt% SiO2, ≥15 wt% Al2O3, and has a particle size of less than 325 mesh; the aerated concrete waste is composed of tobermorite, semi-crystalline CSH(I), CSH gel, and silica, and is pulverized and ground to a fineness of less than 600 mesh; the dispersing stabilizer is a mixture of ketal-aldehyde condensate and microcrystalline cellulose.

[0028] The active component A of this invention utilizes carbide slag, biomass slag, and aerated concrete waste under wet grinding conditions to generate hydrated calcium silicate and hydrated calcium aluminosilicate. The aerated concrete waste contains a large amount of tobermorite, which can serve as nucleation sites for calcium silicate and hydrated calcium aluminosilicate, greatly accelerating the formation of hydrated calcium silicate and hydrated calcium aluminosilicate and promoting the cement hydration reaction.

[0029] Preferably, the active component B is a mixture of modified zirconium silicon slag, silicomanganese slag, phosphorus slag and alkali slag in a mass ratio of 3:2:1:1. The modified zirconium silicon slag is made into slurry C from zirconium silicon slag. Slurry C is neutralized, washed with water, and impurity removed, and then subjected to solid-liquid separation. The product is obtained by high-temperature drying and grinding.

[0030] More preferably, the modified zirconium silicon slag has a SiO2 content ≥90wt%, a neutral pH, and a powder particle size of less than 325 mesh; the ferromanganese slag has a powder particle size of less than 325 mesh, a SiO2 content of 35-40wt%, an Al2O3 content of 9-12wt%, a CaO content of 25-28wt%, and a MgO content of 6-11wt%; the phosphorus slag has a SiO2 content of 35-40wt% and a CaO content of 42-48wt%; and the alkali slag has a CaCO3 content of 40-45wt%, a CaSO4 content of 7-10wt%, and a CaCl2 content of 10-14wt%.

[0031] The active component B of this invention contains a large number of amorphous SiO2 particles, which are highly active and can quickly react with the cement hydration product Ca(OH)2 to accelerate cement hydration. At the same time, the active component B also contains a small amount of MgO and CaSO4, which can promote the crystallization of ettringite through synergistic effect with the reinforcing component, and can also form Mg(OH)2 during cement hydration, thereby enhancing the bonding and sealing properties of the cementing stone and improving the anti-channeling ability of the cementing stone.

[0032] Preferably, the reinforcing component is composed of lithium silicate and aluminum sulfate mixed in a mass ratio of 1:2;

[0033] More preferably, the purity of the lithium silicate is greater than 98 wt%, and the purity of the aluminum sulfate is greater than 98 wt%.

[0034] The reinforcing component of this invention can react with free hydroxide ions (OH-). - ) and calcium ions (Ca) in the system 2+ The reaction produces silicate cement and calcium silicate, which fill the micropores and gaps in the hydration products, thereby increasing the matrix density. The generated silicate cement and calcium silicate, through a synergistic effect with active component A, further promote the formation of hydrated calcium silicate and hydrated calcium aluminosilicate; the reinforcing component also works with various ions released by active component B to promote the crystallization of ettringite. Due to the large amount of Si in the system... 4+ Al 3+ and Ca 2+ The consumption of plasma further promotes cement hydration and the dissociation and release of active component B, thereby promoting early strength formation. In addition, the Li released by lithium silicate... + It accelerates the destruction of the early hydration product film covering cement particles, thus speeding up the hydration process.

[0035] Furthermore, the elastic and tough material is made by mixing ethylene-butyl acrylate copolymer and cellulose acetate butyrate in a mass ratio of 5:2 after being pulverized into fine powder, and then modified by low-temperature plasma.

[0036] Furthermore, the ethylene-butyl acrylate copolymer contains 33-37 wt% butyl acrylate; the cellulose acetate butyrate contains 12-15 wt% acetyl groups and 32-35 wt% butyryl groups.

[0037] Furthermore, the micro-expansion material is a mixture of hydropyrite and magnesite tailings in a mass ratio of 1:3; preferably, the hydropyrite contains >99wt% lithium magnesium silicate; and the magnesite tailings contain 38-42wt% MgO and 15-18wt% SiO2.

[0038] Furthermore, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 The Dv50 is 40μm and the compressive strength is >4000psi; the water loss reducing agent is 2-acrylamido-2-methylpropanesulfonic acid / acrylamide copolymer; the dispersant is sulfonated acetone formaldehyde condensate.

[0039] On the other hand, the present invention also provides a method for preparing cement suitable for cementing coalbed methane wells. The preparation method is as follows: G-grade cement, active mineral materials, composite reinforcing materials, weight-reducing agents, fluid loss reducing agents and dispersants are mixed evenly in proportion to form dry powder, thereby obtaining cement suitable for cementing coalbed methane wells.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The cement for coalbed methane cementing of this invention exhibits excellent workability under low-temperature conditions, rapid strength development, good anti-channeling performance, and good toughness. Furthermore, this invention uses a large amount of solid waste as raw material, increasing the amount of solid waste disposed of and reducing the waste of land resources and environmental pollution caused by solid waste stockpiling. It is characterized by being green, environmentally friendly, and low-cost.

[0042] 2. The composite reinforcing material of this invention provides an alkaline environment for the initial hydration reaction of cement, which on the one hand promotes the cement hydration reaction and reacts with the SO4 dissolved from itself. 2- Together they promote the formation of hydration products such as ettringite; on the other hand, they provide hydrated calcium silicate and hydrated calcium aluminosilicate seed crystals for the early stage of cement hydration, providing a good nucleation effect during the cement hydration process, inducing the formation of hydrated calcium silicate and hydrated calcium aluminosilicate during the cement hydration process, further promoting cement hydration and thus improving the early strength of cement.

[0043] 3. The composite reinforcing material of the present invention is made by blending ethylene-butyl acrylate copolymer and cellulose acetate butyrate after crushing and mixing them in a Z-type kneader. Under strong shearing and thermal effects, the resulting elastic-tough material has improved elasticity, toughness and strength. The surface of the elastic-tough material is modified by low-temperature plasma, which improves the surface tension and hydrophilicity of the elastic-tough material, enhances the bonding between the elastic-tough material and cement in the transition zone and the internal pore structure, and the surface of the elastic-tough material is covered with hydration products, resulting in stronger bonding with the cement matrix.

[0044] 4. The composite reinforcing material of this invention, through the combined effect of hydropyrite and magnesite tailings, not only improves the stability of cement paste and reduces its water loss, but also enhances the bonding properties between cement hydration products, increases the density of the cement system, and thus improves its strength development. Furthermore, the Mg(OH)2 formed by hydration in the alkaline environment provided by the early-strength material of this invention, together with the ettringite generated under the promoting effect of the early-strength material, synergistically enhances the expansibility of the cementitious stone, improves its bonding and sealing properties, and thus enhances the anti-channeling ability of the cementitious stone. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] In this embodiment of the invention, Grade G cement is provided by Jiahua Special Cement Co., Ltd.; the water loss reducing agent is 2-acrylamido-2-methylpropanesulfonic acid / acrylamide copolymer; and the dispersant is sulfonated acetone formaldehyde condensate.

[0047] Example 1

[0048] As a preferred embodiment of the present invention, the specific composition of the cement suitable for cementing coalbed methane wells in this embodiment is shown in Table 1 below:

[0049] Table 1

[0050] raw material Weight percentage (wt%) Grade G cement 55 Active mineral materials 20 Composite reinforced materials 5 Relief agent 15 Water loss reducer 3 dispersant 2

[0051] In this embodiment, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:1.

[0052] In this embodiment, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of 14:3:3.

[0053] In this embodiment, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 Dv50 has a diameter of 40μm and a compressive strength of >4000psi.

[0054] After weighing G-grade cement, active mineral materials, composite reinforcing materials, fiber materials, weight-reducing agents, fluid loss reducing agents, and dispersants according to the weight ratios in Table 1, the raw materials are mixed evenly to obtain cement #1 for cementing.

[0055] Cement slurry was prepared using cement #1 for cementing in accordance with GB / T19139 standard, with a water-cement ratio of 0.6, resulting in cement slurry system #1 for cementing.

[0056] Example 2

[0057] As a preferred embodiment of the present invention, the specific composition of the cement suitable for cementing coalbed methane wells in this embodiment is shown in Table 2 below:

[0058] Table 2

[0059] raw material Weight percentage (wt%) Grade G cement 65 Active mineral materials 17.5 Composite reinforced materials 4 Relief agent 10 Water loss reducer 2 dispersant 1.5

[0060] In this embodiment, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:1.

[0061] In this embodiment, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of 14:3:3.

[0062] In this embodiment, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 Dv50 has a diameter of 40μm and a compressive strength of >4000psi.

[0063] After weighing G-grade cement, active mineral materials, composite reinforcing materials, fiber materials, weight-reducing agents, fluid loss control agents, and dispersants according to the weight ratios in Table 2, the raw materials are mixed evenly to obtain cement #2 suitable for cementing.

[0064] Cement slurry was prepared using cement #2 for cementing in accordance with GB / T19139 standard, with a water-cement ratio of 0.6, resulting in cement slurry system #2 for cementing.

[0065] Example 3

[0066] As a preferred embodiment of the present invention, the specific composition of the cement suitable for cementing coalbed methane wells in this embodiment is shown in Table 3 below:

[0067] Table 3

[0068]

[0069]

[0070] In this embodiment, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:1.

[0071] In this embodiment, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of 14:3:3.

[0072] In this embodiment, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 Dv50 has a diameter of 40μm and a compressive strength of >4000psi.

[0073] After weighing the G-grade cement, active mineral materials, composite reinforcing materials, fiber materials, weight-reducing agents, fluid loss reducing agents, and dispersants according to the weight ratios in Table 3, the raw materials are mixed evenly to obtain cement #3 for cementing.

[0074] Cement slurry was prepared using cement #3 for cementing in accordance with GB / T19139 standard, with a water-cement ratio of 0.6, resulting in cement slurry system #3 for cementing.

[0075] Example 4

[0076] As a preferred embodiment of the present invention, the specific composition of the cement suitable for cementing coalbed methane wells in this embodiment is shown in Table 4 below:

[0077] Table 4

[0078] raw material Weight percentage (wt%) Grade G cement 75 Active mineral materials 15 Composite reinforced materials 3 Relief agent 5 Water loss reducer 1 dispersant 1

[0079] In this embodiment, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:1.

[0080] In this embodiment, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of 16:3:3.

[0081] In this embodiment, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 Dv50 has a diameter of 40μm and a compressive strength of >4000psi.

[0082] After weighing the G-grade cement, active mineral materials, composite reinforcing materials, fiber materials, weight-reducing agents, fluid loss control agents, and dispersants according to the weight ratios in Table 4, the raw materials are mixed evenly to obtain cement #4 for cementing.

[0083] Cement slurry was prepared using cement #4 for cementing according to GB / T19139 standard, with a water-cement ratio of 0.6, resulting in cement slurry system #4 for cementing.

[0084] Example 5

[0085] As a preferred embodiment of the present invention, the specific composition of the cement suitable for cementing coalbed methane wells in this embodiment is shown in Table 5 below:

[0086] Table 5

[0087] raw material Weight percentage (wt%) Grade G cement 75 Active mineral materials 15 Composite reinforced materials 3 Relief agent 5 Water loss reducer 1 dispersant 1

[0088] In this embodiment, the active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:1.

[0089] In this embodiment, the composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of 8:1:1.

[0090] In this embodiment, the weight-reducing agent is hollow glass microspheres with a density of 0.44–0.48 g / cm³. 3 Dv50 has a diameter of 40μm and a compressive strength of >4000psi.

[0091] After weighing the G-grade cement, active mineral materials, composite reinforcing materials, fiber materials, weight-reducing agents, fluid loss control agents, and dispersants according to the weight ratios in Table 5, the raw materials are mixed evenly to obtain cement #5 for cementing.

[0092] Cement slurry was prepared using cement #5 for cementing according to GB / T19139 standard, with a water-cement ratio of 0.6, resulting in cement slurry system #5 for cementing.

[0093] Comparative Example 1

[0094] Except for the absence of lepidolite ore slag and wollastonite powder in the active mineral materials, this comparative example is the same as Example 1, yielding cement 1* for cementing and cementing slurry system 1*.

[0095] Comparative Example 2

[0096] Except for the absence of early-strength materials in the composite reinforcing material, this comparative example is the same as Example 1, yielding cement 2* for cementing and cementing slurry system 2*.

[0097] Comparative Example 3

[0098] Except for the absence of elastic and tough materials in the composite reinforcing material, this comparative example is the same as Example 1, resulting in cement 3* for cementing and cementing slurry system 3*.

[0099] Comparative Example 4

[0100] Except for the absence of micro-expansion materials in the composite reinforcing material, this comparative example is the same as Example 1, yielding cement 4* for cementing and cementing slurry system 4*.

[0101] Test case

[0102] 1. Referring to GB / T19139 Oil Well Cement Test Method, the engineering performance of the cement slurry systems prepared by Comparative Examples 1 to 4 and Examples 1 to 5, including density, water loss, fluidity, anti-channeling coefficient, thickening time, etc., were tested. The results are shown in Table 6.

[0103] Table 6

[0104]

[0105] According to the data in Table 6, the cement slurry systems prepared in Examples 1 to 5 have a slurry water loss of less than 40 ml and a fluidity of greater than 18 cm, which can well meet the construction requirements. Furthermore, they have low SPN values ​​(anti-channeling coefficients), indicating excellent anti-channeling ability, and significantly shortened thickening time. Compared with Example 1, the engineering properties of the cement slurry systems in Comparative Examples 1 to 4 showed varying degrees of decline.

[0106] 2. The compressive strength and elastic modulus of the cement slurry systems prepared by Comparative Examples 1 to 4 and Examples 1 to 5 were tested according to GB / T19139 Test Method for Cement in Oil Wells. The results are shown in Table 7.

[0107] Table 7

[0108]

[0109] As shown in Table 7, the cement slurry system prepared in this embodiment of the invention can rapidly hydrate and develop strength at low temperatures, which is beneficial for shortening the cementing time in shallow oil and gas wells. Furthermore, the elastic modulus indicates that this invention effectively improves the toughness of cementing cement, resulting in cement stone with excellent toughness, meeting the performance requirements of cement slurry in low-temperature cementing projects and effectively solving the problem of insufficient toughness of cement stone under low-temperature conditions.

[0110] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A cement suitable for cementing coalbed methane wells, characterized in that, The following raw materials are included by weight percentage: Grade G cement: 55-75 wt%; Active mineral materials: 15-20 wt% Composite reinforcement material: 3-5 wt% Reducer: 5-15 wt% Water loss reducer: 1~3wt%; Dispersant: 1~2wt%; The active mineral material is a mixture of fly ash, microsilica, lithium mica ore slag and wollastonite powder in a mass ratio of 3:2:1:

1. The composite reinforcing material is a mixture of early strength material, elastic toughness material and micro-expansion material in a mass ratio of (14~16): (2~3): (2~3); The early strength material is composed of active component A, active component B and reinforcing component mixed in a mass ratio of 1:3:1; The active component A is composed of calcium carbide slag, biomass slag and aerated concrete waste in a mass ratio of 5:4:

1. The active component B is composed of modified zirconium silicon slag, ferromanganese slag, phosphorus slag, and alkali slag mixed in a mass ratio of 3:2:1:

1. The reinforcing component is composed of lithium silicate and aluminum sulfate mixed in a mass ratio of 1:2; The elastic and tough material is made by mixing ethylene-butyl acrylate copolymer and cellulose acetate butyrate in a mass ratio of 5:2 after being pulverized into fine powder, and then modified by low-temperature plasma. The micro-expansion material is a mixture of hydropyroxene and magnesite tailings in a mass ratio of 1:

3.

2. The cement for cementing coalbed methane wells according to claim 1, characterized in that, The fly ash contains 40-50 wt% SiO2 and 35-45 wt% Al2O3; the microsilica contains 96 wt% SiO2 and has a particle size of 0.05-0.30 μm; the lithium mica ore slag contains 50-60 wt% SiO2, 25-30 wt% Al2O3, and 3-5 wt% CaSO4; the wollastonite powder contains >50 wt% SiO2, >40 wt% CaO, and has an average particle size of 50 μm.

3. The cement for cementing coalbed methane wells according to claim 1, characterized in that, The method for preparing the early strength material is as follows: S1. Mix the active component A and the reinforcing component to obtain powder A; S2. Place active component B in a ball mill jar and ball mill at 500 rpm for 6 hours to obtain powder B; S3. Powder A and powder B are pneumatically mixed to obtain an early-strength material.

4. A cement suitable for cementing coalbed methane wells according to claim 3, characterized in that, The preparation method of the active component A is as follows: S11. Place carbide slag, biomass slag and aerated concrete waste in a ball mill jar at a mass ratio of 5:4:1, with a liquid-to-material ratio of 1.0, and ball mill at 400 rpm for 72 hours to obtain slurry A. S12. Place slurry A in a sealed mixing tank, add 1 wt% of the dispersant and stabilizer from the solid phase of slurry A and stir. The stirring temperature is 80℃ and the stirring time is 72h to obtain slurry B. S13. Place slurry B in a centrifuge for liquid-solid separation, and dry the solid phase at the bottom of the liquid-solid separation into dry powder to obtain active component A.

5. A cement suitable for cementing coalbed methane wells according to claim 4, characterized in that, The carbide slag contains 65-70 wt% CaO and has a pH of 12-13; the biomass slag contains ≥65 wt% SiO2, ≥15 wt% Al2O3, and has a particle size of less than 325 mesh; the aerated concrete waste is composed of tobermullite, semi-crystalline CSH(I), CSH gel, and silica, and is pulverized and ground to a fineness of less than 600 mesh; the dispersing stabilizer is a mixture of ketaldehyde condensate and microcrystalline cellulose.

6. A cement suitable for cementing coalbed methane wells according to claim 1, characterized in that, The modified zirconium silicon slag is made into slurry C from zirconium silicon slag. Slurry C is neutralized, washed with water, and impurity removed, then subjected to solid-liquid separation, and finally dried and ground at high temperature to obtain the product.

7. A cement suitable for cementing coalbed methane wells according to claim 1, characterized in that, The modified zirconium silicon slag has a SiO2 content ≥90wt%, a neutral pH, and a powder particle size less than 325 mesh; the ferrosilicon manganese slag has a powder particle size less than 325 mesh, a SiO2 content of 35~40wt%, an Al2O3 content of 9~12wt%, a CaO content of 25~28wt%, and a MgO content of 6~11wt%; the phosphorus slag has a SiO2 content of 35~40wt% and a CaO content of 42~48wt%; the alkali slag has a CaCO3 content of 40~45wt%, a CaSO4 content of 7~10wt%, and a CaCl2 content of 10~14wt%; the lithium silicate has a purity greater than 98wt%; and the aluminum sulfate has a purity greater than 98wt%.

8. A cement suitable for cementing coalbed methane wells according to claim 1, characterized in that, The ethylene-butyl acrylate copolymer contains 33-37 wt% butyl acrylate; the cellulose acetate butyrate contains 12-15 wt% acetyl groups and 32-35 wt% butyryl groups.

9. A cement suitable for cementing coalbed methane wells according to claim 1, characterized in that, The hydropyrite contains >99wt% lithium magnesium silicate; the magnesite tailings contain 38-42wt% MgO and 15-18wt% SiO2.

10. A cement suitable for cementing coalbed methane wells according to claim 1, characterized in that, The weight-reducing agent is hollow glass microspheres with a density of 0.44~0.48 g / cm³. 3 The Dv50 is 40μm and the compressive strength is >4000psi; the water loss reducing agent is 2-acrylamido-2-methylpropanesulfonic acid / acrylamide copolymer; the dispersant is sulfonated acetone formaldehyde condensate.

11. A method for preparing cement suitable for coalbed methane cementing according to any one of claims 1 to 10, characterized in that, The preparation method is as follows: G-grade cement, active mineral materials, composite reinforcing materials, weight-reducing agents, fluid loss reducing agents and dispersants are mixed evenly in proportion to form dry powder, which is the cement suitable for cementing coalbed methane wells.

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